1. Field of the Invention
The present invention pertains to routing cable within existing pipelines, and to apparatus suitable for use therein.
2. Background Art
In rural environments, routing of a variety of cable, particularly communications cable, may be accomplished by overhead routing on “telephone” poles or by routing underground in newly installed conduits or tunnels. In suburban environments, both overhead and underground routing is also commonplace, the latter particularly in the case of new construction.
In urban environments, however, cable routing is a difficult feat. Often, overhead routing lines are either non-existent, or are already used to full capacity. Underground routing is exceptionally expensive, when available at all, since adding additional tunnels or conduit often involves tearing up lengthy expanses of street or pavement. Boring machines are generally not practical, as the subsurface is already laced with numerous tunnels, conduits, subways, water lines, sewer lines, gas lines, and the like. Thus, a cost-effective method of routing additional cables of any type in urban environments is very desirable.
Use of existing infrastructure, for example water and sewer lines, particularly the latter, has been proposed. However, cable cannot merely be introduced into such environments and left to freely move. Continuous movement over long periods can generate fatigue and work-hardening in metal conductor-containing cables. Sudden movements or the development of sharp bends or kinks can be destructive of fiber optic cables. Moreover, despite the numerous advances in cable insulation, covering, and armor, it is still not desirable, as a general rule, that the cable be continually immersed in liquid. For these reasons, it is desired to route, or “string” the cables in the topmost position of the pipeline where exposure to liquids is minimized to the extent possible, and, if possible, to enclose the cable in protective conduit.
In order to accomplish these aims, several methods have been proposed. In copending U.S. application Ser. No. 09/679,987 filed Oct. 5, 2000, it is proposed to employ an otherwise conventional pipeline relining procedure using a thermoplastic or thermosetting liner, this liner also having integral cable conduit(s) as supplied, and as illustrated in FIG. 2. By this procedure, it is possible to supply one or more cable conduits during the relining process. The conduits are fixed in position, and the conduit interiors are preferably isolated from the liner interior, to prevent or minimize contact of cable with pipeline fluids. This method is very cost-effective where pipeline renovation by relining is mandated. However, the method is not satisfactory for pipelines which are not totally in need of renovation.
It has been proposed to install “J-hooks” in the ceiling of sewer lines, the J-hooks carrying conduit or cable, as disclosed in FIG. 1. Installation of the J-hooks is problematic, however. Each hook requires drilling a hole into the existing pipeline, and securing the J-hook with an expandable lead “anchor” or by using a cementitious or adhesive grout. Due to the nature of sewer pipe material of construction and its constant exposure to wet or moist environments, many installation failures are to be expected, as is also occasional damage to the pipe itself, including perforation, cracking, etc. Installation is a slow process. Moreover, due to little support in directions transverse to the stem of the J-hook stem, the hooks may be removed by occasional passage of obstructions down the pipe, or by collision with sewer cleaning or renovating robots, etc.
It has been reported in the New York Times, Mar. 8, 2001, pp. G1 and G7, that Ka-Te System A.G. has developed a robotic system for installing bands resembling hose clamps, these bands having clamps mounted thereon to mount conduit. However, the robotic system for expanding the bands is complex and expensive, the bands provide little lateral support, and thus are subject to cocking out of position. Due in part to this lack of lateral support, bands must be installed close together in order to provide the necessary degree of support for the conduit.
It would be desirable to provide a method for routing cables which is cost-effective, which has little if any chance to damage the pipeline during installation, and which provides sufficient lateral support for the cable or conduit-receiving means that occasional passage of bulky materials or collision with pipeline cleaning equipment, etc., will not cause failure of the support means. It would be further desirable in preferred embodiments to provide a means of routing cables and/or conduit through existing pipelines which does not require pipeline relining, or the boring of numerous holes for discrete support hooks or other devices.